The present invention relates to a safety switching device module arrangement comprising at least one input module for processing signals from a safety transmitter and for generating output signals, and comprising at least two output modules for driving an actuator, wherein the input module and the output modules are arranged in a series forming a series of modules, and wherein the input module is associated to at least one output module.
Safety switching devices are generally known. They are used to fail-safely analyze the signals from a safety transmitter, as for example an emergency off switch, a protective door position switch etc., and to drive one or more fail-safe output contacts of an output circuit. Actuators, such as contactors, valves, motors, and hazardous machine parts such as saw blades, robot arms, high-voltage equipment, etc., are transferred into a safe state by these output contacts then. The present assignee offers a large number of different types of safety switching devices under the common tradename xe2x80x9cPNOZxe2x80x9d. Furthermore, in xe2x80x9cMaschinensicherheitxe2x80x9d [Machine safety], Winfried Grxc3xa4f, Hxc3xcthig Verlag, 1997, several variations of safety switching devices are illustrated. A specific safety switching device is also disclosed by DE 197 36 183 C1.
In practice, it very often occurs that a plurality of switching events, for example the actuation of an emergency off switch, the opening of a door or reaching through a light curtain, have to be AND-linked, for example. For this purpose, a plurality of switching devices are connected in series, the output terminals of one safety switching device being connected to the input terminals of the following safety switching device.
In many cases, in addition to the AND linking, a hierarchical structure of the safety switching devices is desired, in order, for example in one case, to stop the entire machine with a single switching event, such as an emergency off switch, and in order to stop only a specific motor of the complete machine with other switching events, such as protective door switches. Such a hierarchical structure has hitherto been possible by appropriate wiring and it has been proved successful in practice.
Nevertheless, there remains a desire to provide a simpler and less expensive structure without any deterioration in safety.
in view of the above, it is an object of the present invention to provide a safety switching device module arrangement which allows for a flexible linking of the safety switching devices used without having to perform external wiring of the individual safety switching devices.
This object is achieved according to one aspect of the invention by a safety switching device module arrangement as mentioned at the outset, wherein the association of the input module to the first, the second or both output modules is achieved on the basis of the position of the input module within the series of modules.
With the inventive safety switching device module arrangement, it is possible to select the association of the input module to one or both output modules by the input module being placed at a specific position within the series of modules. Within this context, the term xe2x80x9cassociationxe2x80x9d is to be understood to mean that there is a signal connection of direct or indirect type between the input module and the xe2x80x9cassociatedxe2x80x9d output module, so that the output module controls the connected actuator in response to the output signal from the associated input module.
The user of the safety switching device module arrangement is therefore in the position to modularly build up a system in accordance with his needs, and he can freely select the association of the input modules to the output modules and therefore the linking of the signals from the safety transmitters. The input module can act on the first output module, on the second output module or on both output modules depending on its position within the series of modules. An (associated) input module acting on both output modules serves for the central actuation of both output modules, while the association of an input module to an individual output module actuates only the latter.
Consequently, the inventive safety switching device module arrangement makes it possible for the user to have a very flexible and simple structure of a safety switching device system, in which the safety switching devices can be linked differently to one another, the linking itself being defined by the corresponding selection of the position of the input module within the series of modules, without having to make any changes in the wiring.
In a refinement of the invention, at least three input module places are provided each to accommodate an input module, and at least a first and a second output module place are provided each to accommodate an output module, at least one input module place being associated to the first output module place, at least a further input module place being associated to the second output module place, and at least another input module place being associated to both the first and to the second output module place.
In a configuration, fixed input module places are provided, for example in a housing, which are connected to output module places, for example by a fixed wiring. By using an association table, the user can assign input modules to specific output modules in accordance with his needs by selecting the appropriate input module places. Owing to the fixed association of input module places to output module places, a simple structure can be implemented, which manages without control modules, etc.
In another refinement of the invention, each input module place has an output terminal and each output module place has an input terminal, a wiring, preferably an electrical connection, being provided between the respective output terminal of the input module place and the input terminal of the output module place in accordance with the association of input module places to output module places.
These measures have the advantage that a fail-safe, software-independent, and permanently wired solution is provided, in which the association of individual module places for input modules to module places for output modules is predefined permanently, therefore being simple to handle and cost-effective. Although there is permanent wiring, a very flexible system of safety switching devices is built up, but the possibilities of associations are restricted by the fixed wiring. However, in many cases, such a solution is sufficient for the requirements placed.
In another refinement of the invention, a control module is provided, which controls the association of input modules and output modules.
This measure has the advantage that the predefined limits on flexibility in the permanently wired solution are overcome. Rather, the control module allows any desired association of input modules to output modules. The control module preferably comprises a control device having a memory unit, in which an association table defining the association is stored. The control device is preferably implemented as a microprocessor or microcontroller, and a data busxe2x80x94preferably a serial data bus, for example a serial optical data busxe2x80x94provides the connection between the control device and the module places.
The latter measures particularly provide the advantage that the module arrangement can be scaled very easily by adding further modules. The new modules merely have to be attached to the existing data bus.
Another increase in the flexibility of the overall system is achieved when the control device comprises a detection unit which detects a positioning of the modules within the series of modules, wherein an absolute association table is determined on the basis of the placing of the output modules and on the basis of a relative association table. This means that the association table initially contains an association of module places within the series of modules relative to the output modules. For example, the relative association table could contain the association that all modules on the left beside an output module are associated to the latter, and all the modules on the right of the final right output module are associated to all the output modules. By using the occupancy of the module places within the series of modules by input and output modules, the control device can then determine, on the basis of the relative association table, an absolute association table, in which the association is stored in absolute values, that is to say, for example, module 1 acts on module 4, etc.
These measures lead to an even more increased flexibility and freedom in the construction of a modular safety switching device system, which, additionally, can also be scaled very easily. An input unit is preferably provided, which permits the association table to be edited, so that yet another increase in the flexibility of the overall system is achieved.
The input modules are preferably input circuits of the kind known from safety switching devices, i.e. those switching circuits which evaluate the signals from safety transmitters in a fail-safe manner. The output circuits preferably comprise the output contacts of safety switching devices, i.e. switches which operate electromechanically or electronically and which are actuated by the output signals from the input circuits. In this case, the output circuits are also constructed in a fail-safe manner. In this connection, it will be appreciated that a fail-safe construction can be achieved, for example, by providing two independent channels or one channel plus a checking unit.
Further advantages and refinements of the invention emerge from the description and the appended drawing.
It goes without saying that the features mentioned above and those following and still to be explained can be used not only in the respectively specified combination but also in other combinations or on their own without departing from the scope of the present invention.